One example of a known conventional sealing device provided with a floating ring is illustrated in FIG. 7 (hereinafter referred to as the first prior art; for example, see Patent Document 1). In the first prior art, interconnecting parts 36 oriented radially outward are provided to an outer periphery of a floating ring 35 formed in an annular shape. The interconnecting parts 36 are provided as a pair at a 180° interval in the circumferential direction and are inserted into a groove part 38 of a casing 37, thus supporting the floating ring 35 so as to be concentric with a rotating shaft 39.
A different example of another known conventional sealing device provided with a floating ring is illustrated in FIG. 8 (hereinafter referred to as the second prior art; for example, see Patent Document 2). The second prior art is provided with: a rotating shaft 40; a cylindrical casing 42 mounted onto a pump main body 41; a sealing liquid supply port 43 provided so as to penetrate through the pump main body 41 and the cylindrical casing 42; a retainer 44 provided to an inner side of the cylindrical casing 42; an annular floating ring 45 installed on an inner side of the retainer 44; and a rotation-blocking pin 46 provided between the floating ring 45 and the retainer 44. A water film formed in a gap a between an inner peripheral surface of the floating ring 45 and an outer peripheral surface of the rotating shaft 40 allows the floating ring 45 to avoid contact with the rotating shaft 40; also, the floating ring 45 is held and self-aligned so as to be able to float in a direction perpendicular to the radius.
In the sealing device provided with the floating ring in the first prior art illustrated in FIG. 7, the floating ring 35 will not rotate, because the interconnecting parts 36 provided as a pair at a 180° interval in the circumferential direction are inserted into the groove part 38 of the casing 37. However, in practice, it is difficult to assemble the floating ring 35 to be concentric with the rotating shaft 39, and therefore a problem is presented in that the floating ring 35 is assembled in an eccentric state relative to the rotating shaft 39. An additional problem has been presented in that the floating ring 35 is unable to flexibly track the eccentricity of the rotating shaft 39 caused by the deflection of the rotating shaft 39 or a similar factor.
In the sealing device provided with the floating ring in the second prior art illustrated in FIG. 8, although the water film formed in the gap a between the inner peripheral surface of the floating ring 45 and the outer peripheral surface of the rotating shaft 40 provisionally allows the floating ring 45 to be self-aligned, the gap a formed between the inner peripheral surface of the floating ring 45 and the rotating shaft 31 will not be uniform in a case where the dynamic pressure generated at the portion where the gap between the inner peripheral surface of the floating ring 45 and the rotating shaft 40 is small is less than the weight of the floating ring 45, and thus operation will take place in an eccentric state.